In electronic equipment such as disc drive data storage systems, the demand for additional power, in both the speed at which they process data and the amount of data they can process, has resulted in a growth in the functionality and an increase in the complexity of these devices. Printed circuit boards (PCBs) or printed circuit board assemblies (PCBAs) employed in such complex electronic devices include several electrical components, such as integrated circuit chips, that manage the operations of these devices. Several areas on a PCB, such as areas that surround integrated circuit chips, include a large number of closely spaced electrical points or nodes that serve as means for electrically coupling to the chips. Thorough electrical inspection or testing of these complex PCBs is required during the assembly of electronic devices that employ the PCBs.
Testing of a PCB usually involves making contact with each electrical point on a circuit and monitoring each and every circuit component and each and every circuit path. In this manner, opens, shorts, missing components, wrong components, backwards and improperly installed components, and out of tolerance components can be individually identified. An array of conductors or pointed probe tips sometimes referred to as a “bed of nails,” which can contact various test points on the PCB are used to interface electrical test equipment to the PCB to be tested. These probes are typically spring loaded and have first ends that are usually mounted on a probe support plate through which they electrically couple to test equipment and second ends that can provide electrical contact to PCB test points. The PCB to be tested is positioned on a mounting plate, which is disposed opposite and substantially parallel to the probe support plate. The probe support plate and/or the mounting plate can be moved in a direction perpendicular to the plates to urge the probe tips against the test points of the PCB during a testing operation. The movement of the probe support plate and/or the mounting plate is carried out by an actuator that can comprise any suitable hydraulic or pneumatic piston and cylinder unit.
One PCB test fixture employs a mounting plate that is only centrally supported by a support member that extends from the base of the test fixture. When relatively large PCBs are mounted and tested on PCB test fixtures that include such centrally supported mounting plates, forces applied near the edges and corners of the PCB when test probes are urged against test points on the PCB can cause the mounting plate and the PCB to tilt. Such tilting can result in loss of electrical contact between one or more test probes and the PCB test points to thereby destroy electrical continuity and thus provide incorrect test results.
Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.